1. Field of the Invention
The present invention relates, in general, to a multi-mode SCSI backplane, and to configuration logic that detects whether the SCSI backplane is configured for simplex or duplex mode, and also detects illegal cabling configurations.
2. Relevant Background.
The SCSI (small computer system interface) connection interface provides a fast, versatile way for PCs and servers to connect with a variety of storage devices including hard disk drives (HDDs), optical drives, and tape drives, among others. A common configuration for SCSI interfaces in servers includes a SCSI circuit board known as a backplane that typically includes SCSI connectors. In a typical configuration, the SCSI backplane is internal to a server box, and interfaces with the main motherboard of the server via a cabled SCSI connection. The SCSI controller circuitry is typically located on the server motherboard, the SCSI backplane, or both boards.
Multi-mode SCSI backplanes are designed to support multiple connection configurations including simplex mode configuration and duplex mode configuration. While multi-mode SCSI backplanes have the advantage of supporting multiple configuration modes on a single SCSI backplane, they also have added expense and design complications. For example, multi-mode SCSI backplanes typically have to incorporate complex logic such as Programmable Array Logic (PALs) in the backplane. Furthermore, multi-mode SCSI backplanes often use sideband signals through additional connector interfaces external to the SCSI interface.
Another problem occurs when an operator incorrectly attempts to connect peripheral devices to the SCSI backplane. These so called illegal configurations include illegal cabling configurations and improper termination of connectors that are not in use, among other errors. Illegal configurations can cause the SCSI interface to malfunction and may even result in permanent circuit damage.